This invention relates to storage and in preferred embodiments relates to the art of cold storage, including appliances such as refrigerators and freezers for storing foodstuffs and other perishables. Other applications of the invention include storage of chemicals and medical or biological specimens. The invention also finds use in mobile applications, for example in the transport and storage of perishable goods. More generally, the invention finds use in any form of storage involving the use of drawers, but particularly where the drawers need to be sealed when closed.
The invention finds particular benefit in the context of the Applicant's multi-compartment cold storage appliances of the general type disclosed in its co-pending patent applications WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107, the contents of which are incorporated herein by reference, and develops and adds to certain features of those specifications while omitting or varying other features. As in those specifications, the invention can be applied to storing any items whether within a cooled environment or otherwise. The term ‘appliance’ is therefore to be construed broadly, extending beyond fixed domestic devices into industrial, scientific and mobile applications. However, this specification will particularly describe domestic or commercial cold-storage appliances for storing foodstuffs.
The compartments of the appliances disclosed in WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107 are drawers sealed from one another to minimise cross-contamination, waste of energy and icing. Optionally, there is provision to select different temperatures in different compartments to suit different foodstuffs or other contents, and to suit different cold-storage regimes such as refrigeration marginally above zero Celsius and freezing significantly below zero Celsius. Indeed, it is possible for a given compartment to be converted readily from refrigerator to freezer and back again, thereby to vary the proportion of refrigerator space to freezer space in the appliance as a whole. In this way, the appliance can respond to changing cold-storage needs.
Briefly to recap the introduction of WO 01/020237, the advantages of storing foodstuffs and other perishable items in refrigerated and segregated conditions have long been known: refrigeration retards the degradation of such items and segregation helps to prevent their cross-contamination. Accordingly, modern cold-storage appliances such as refrigerators and freezers are usually compartmentalised, albeit not often effectively, so that a user can store different types of food in different compartments. All such appliances have the additional aim of maximising their energy efficiency.
The invention herein and the inventions in the Applicant's earlier patent applications WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107 mentioned above were devised against a background of typical cold-storage appliances, most of which comprise one or more upright cabinets each with a vertically-sealed hinged door on its front. Substantially all of the interior of the cabinet defines a storage volume, most commonly partitioned by shelves or drawers for supporting stored foodstuffs. Access to all of the shelves or drawers in the cabinet is gained by opening the door.
A cooler unit generates a convection loop within the cabinet, in which air cooled by the cooler unit sinks toward the bottom of the cabinet and as that air absorbs heat during its downward journey, it warms and rises back up to the cooler unit where it is cooled again. It is also possible to have forced-air circulation by means of a fan within or communicating with the cabinet. The shelves or drawers are typically made of wire so that they offer little resistance to this circulation of air.
WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107 address a major problem with upright refrigerators and freezers, namely the upright door which, when opened, allows cold air to flow freely out of the cabinet to be replaced by warm ambient air flowing in at the top. That rush of ambient air into the cabinet causes its internal temperature to rise, hence consuming more energy in redressing that rise by running the cooler unit. The incoming ambient air introduces the possibility of airborne contamination, and moisture in that air also gives rise to condensation and ice within the cabinet. The more often and frequently the cabinet is opened, as may happen especially in commercial cold storage appliances, the worse these problems get.
In upright-door arrangements, the limitations of the vertical seal mean that loss of cold air and induction of warm air can even occur when the door is closed. Being denser than warmer air, the coldest air collects at the bottom of the cabinet and applies pressure to the sealing interface so that unless the seal forms a perfect seal between the door and the cabinet, that air will escape.
The appliances disclosed in WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107 also address the problems inherent in the well-known chest freezer, whose open-topped cabinet is typically closed by a horizontally-hinged upwardly-opening lid. Such a chest freezer is inconvenient and wasteful of space because it precludes use of the space immediately above the freezer, which space must be preserved to allow its lid to be opened. Even if a sliding lid is used instead of an upwardly-opening lid, items cannot be left conveniently on top of the lid. It is also well known that large chest freezers can make access to their contents extremely difficult, it being necessary to stoop down and shift numerous heavy and painfully cold items to get to items at the bottom of the freezer compartment.
Finally, the appliances disclosed in WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107 address the problem of segregating different types of foodstuff or other perishable items to avoid cross-contamination. In typical cold-storage appliances, segregation of food is compromised by the convection and/or forced-air principles on which those appliances rely. The substantially open baskets or shelves designed to promote convective circulation of air between the compartments also promote the circulation of moisture, enzymes and harmful bacteria. In addition, any liquid that may spill or leak, such as juices running from uncooked meats, will not be contained by the open baskets or shelves.
Conventional cold-storage appliances exemplified by upright refrigerators and chest freezers are not the only prior art disclosures of interest. For example, it has been known for many years to divide a refrigerator into compartments, each with its own dedicated closure such as a door or lid. Examples of this idea are disclosed in UK Patent Nos. GB 602,590, GB 581,121 and GB 579,071, all to Earle, that describe cabinet-like refrigerators.
In those Earle documents, the front of the cabinet is provided with a plurality of rectangular openings for receiving drawers. Each drawer has a front panel larger than its respective opening so that a vertical seal is formed around the overlap when the drawer is in a closed position. The drawers and their contents are cooled by a cooler unit that circulates cooled air by convection within the cabinet, in common with the types of refrigerator already described. To promote circulation of this air amongst all of the drawers, the drawers are open-topped and have apertures in their bottoms. Also, the drawers are disposed in a stepped arrangement, those at the top of the refrigerator extending back less far into the cabinet than the lower drawers so that the rear of each drawer is exposed to the downward flow of cooled air from the cooler unit.
Although only one drawer need be opened at a time, the apertures in the bottom allow cold air to flow freely from the open drawer, which is replaced by warm moist ambient air to the detriment of energy efficiency and with the increased possibility of cross-contamination. Indeed, when a drawer is opened, cold air within the cabinet above the level of that drawer will flood out, drawing ambient air into the cabinet. Furthermore, the drawers encourage ambient air to flow into the interior of the refrigerator because, upon opening, they act as pistons drawing the ambient air into the interior of the refrigerator cabinet. Once in the cabinet, the warm air can circulate as freely as the cold air that is supposed to be there.
Even when closed, the accumulation of cold air towards the bottom of the cabinet will exert increased pressure on the vertical seals of the lowest drawers, increasing the likelihood of leakage if the seal is faulty.
A further example of the above type of refrigerator is disclosed in UK Patent No. GB 602,329, also to Earle. The refrigerator disclosed therein suffers many of the above problems but is of greater interest in that a single drawer consisting of insulated sides and base is provided within the cooled interior of the cabinet. In contrast to the variants outlined above, the sides and base are solid and not perforated so that air cannot flow through them. When the drawer is closed, a horizontal member within the cabinet combines with the drawer to define a compartment, the horizontal member thus being a closure in the form of a lid for the drawer. This compartment is provided with its own cooling coils situated just below the horizontal member.
Very little detail is given about the seal that is formed between the drawer and the horizontal member, other than that the horizontal member has a downwardly projecting rear end with a biased edge that makes a close fit with the rear wall of the drawer. Nothing else is said about the junction between the drawer and the horizontal member, apart from the general statement that the drawer is adapted when in its closed position to fit ‘fairly snugly’ against the horizontal member. It can only be inferred that the drawer and the horizontal member merely abut against each other. Whilst this will impede the passage of air into and out of the drawer, it will not form an impervious seal. As this is not a vapour seal, icing and cross-contamination is likely to occur even when the drawer is closed.
The drawer arrangement described creates a compartment in which a different temperature can be set when compared to the essentially common temperature of the rest of the refrigerator. It is particularly envisaged that the drawer can act as a freezer compartment. The Applicant has appreciated a disadvantage in this arrangement, namely that as the freezer drawer resides within the cooled interior when closed, the outer surfaces of the drawer within the cabinet will be cooled to the temperature of the refrigerator. Accordingly, when the drawer is opened, those cooled outer surfaces will be exposed to ambient air containing moisture that will condense on the cooled surfaces leading to an undesirable accumulation of moisture. Condensation involves transfer of latent heat from water vapour to the drawer, thus increasing the burden of cooling the drawer again when the drawer is returned to the closed position within the cabinet.
Additionally, condensed moisture will be transferred to the interior of the refrigerator when the drawer is closed. As discussed above, the presence of water promotes microbial activity. A further disadvantage of introducing water into the interior of the refrigerator is that it may freeze: this can be a particular problem where the drawer of the enclosed compartment meets the insulated top, as any ice formation will form a seal that locks the drawer in a permanently closed position. This disadvantage was appreciated by Earle, as a cam mechanism is mentioned in GB 602,329 to break any ice formed at the seals or on the runners or other support surfaces of the drawers. It is also possible for a build-up of ice to affect the sealing ability of the seal, by preventing mating sealing surfaces from mating correctly. Of course, the accumulation of ice on moving parts of the drawer mechanism is also undesirable as it will impede movement of the drawer.
A further interesting prior art document, cited as technological background against WO 01/020237, is U.S. Pat. No. 1,337,696 to Ewen. Ewen speaks of segregation between refrigerated drawers contained in a surrounding cabinet and employs refrigerating units placed ‘immediately and closely above each drawer . . . so that said drawer may in effect be said to be closed against said refrigerating unit’. However, there has to be a gap left between the drawer and the refrigerating unit if the drawer is going to open. As in Earle, that gap will promote icing as moist air within the cabinet migrates into the drawer and the water vapour condenses and freezes. The smaller the gap, the sooner the accumulating ice will prevent drawer movement. If a larger gap is tried instead, there will be a greater spillage of air and hence the refrigerator will be less energy-efficient and more susceptible to cross-contamination.
That aside, the spillage of cold air in Ewen lowers the temperature within the cabinet around the drawers, and so increases the likelihood of condensation on the drawers when opened. It will be noted that cold air spilled in this way can fall freely behind the drawers within the cabinet and so expose the exterior of the drawers to air substantially below ambient temperature. Certain design details of Ewen worsen this effect. For example, the bottom wall of the Ewen unit is an efficient insulator which will significantly reduce the surface temperature of the drawers. Also, the internal divisions between the drawers do not allow for ambient heat transfer to the drawers but only for heat transfer between the drawers, thus promoting drawer-to-drawer temperature equalisation over time. Left for long periods, or even overnight, large parts of the external surface of each drawer will fall to temperatures significantly below ambient dew point. Condensation or ice will therefore form on those surfaces as soon as the drawers are opened; similarly, if the drawers are removed and left outside the appliance, they will start to ‘sweat’ with condensation.
Like Earle, opening and closing a drawer within a sealed cabinet in Ewen acts like a piston, alternately applying both negative and positive pressures to adjacent areas. This promotes air transfer through the drawer opening at the front of the cabinet, which can displace cold treated air in a drawer, and within the cabinet itself. An over-sized cabinet would reduce the piston effect but would also be wasteful of space. Conversely, a more space-efficient close-fitting cabinet may decrease the displacement of cold treated air, and so reduce the burden of cooling the warmer air that takes its place, but it will increase resistance to opening and closing the drawer.
Cold air spillage aside, the gap inevitably left between a drawer and its associated lid in prior art arrangements is large enough to allow the passage of enzymes, spores and other airborne contaminants. Also, Ewen discloses a common interconnecting drain and this too would allow free transfer of contaminants between each drawer, particularly under the aforementioned piston action.
Whilst Ewen speaks of different temperatures in different drawers, the plurality of cooling lids are connected in series and have no means for individual temperature control in each drawer. The different temperatures are designed-in by providing some drawers with more cooling elements than others, but there is no measurement or control of those temperatures in use. Also, like the compartments of more conventional prior art, each drawer in Ewen has a fixed function, namely freezer or refrigerator.
It will be apparent from the foregoing that effective sealing is a prerequisite of efficient cold storage whether in appliances having a vertical seal, exemplified by upright-door refrigerators or freezers, or in appliances having a horizontal seal, exemplified by refrigerators or freezers such as a chest freezer.
Traditionally in the refrigeration art, sealing has been achieved by magnetic seals in which, typically, magnetic strips associated with seals around the periphery of an access aperture attract resilient seal parts into mutual sealing contact when the door, lid or other closure of the cold-storage compartment is closed. The seals can be thought of as co-operable sealing loops extending around the aperture and in a corresponding shape and position on the closure, so that the loops come together and align when the closure is closed. Commonly, one sealing loop is a resiliently flexible seal and the other sealing loop is an inflexible sealing surface against which the resiliently flexible seal seats when the door, lid or other closure is closed. However, it is possible for both sealing loops or indeed neither of them to be resiliently flexible seals. It is also possible for both sealing loops to have associated magnetic means or for just one of the sealing loops to have a magnetic means and for the other to include material capable of attraction to a magnet, such as a steel strip extending around the loop.
It is well known that existing magnetic seals are designed to be pushed together and pulled apart, which characteristic is not appropriate for sealing to a lid around the upper periphery of a drawer. It will be apparent that in the case of a drawer, the opening and closing movement of the drawer will involve relative sliding or wiping movement between at least part of the sealing loops. This is because the lid and the upper periphery of the drawer remain in their original planes, albeit subject to relative translation within those planes, as opposed to experiencing angular movement out of their planes which occurs when a traditional lid or door is hinged open. Typical resilient magnetic seals would be expected to deform and wear unacceptably if used in such circumstances, and to present excessive frictional resistance to movement of the drawer.
The Applicant's initial thoughts were that resilient magnetic seals would be inappropriate for use with drawer-type appliances of the general type disclosed in WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107, and in the Earle and Ewen prior art mentioned above. Indeed, the Applicant's objective was to avoid or minimise relative sliding or wiping movement between seal parts whether magnetic or otherwise. Thus, WO 01/020237 and WO 02/073104 propose alternative seal arrangements involving a minor (typically vertical) component of movement of a drawer to separate the drawer from a fixed lid, hence pulling the sealing loops apart, and a major (typically horizontal) component of movement of the drawer to open the drawer fully for access to its contents. When the drawer is being closed, the major component of movement is followed by the minor component to press the sealing loops back together. This two-component movement avoids or minimises relative sliding or wiping movement between parts of the sealing loops.
Whilst the idea of two-component movement of a drawer has proved to be highly effective, the Applicant has continued to explore alternatives. This effort has been particularly focused upon the appliances disclosed in the Applicant's earlier patent applications WO 01/020237, WO 02/073104, WO 02/073105 and WO 02/073107, in which much of the exterior of the drawers and hence the outside of the drawer/lid interface may be exposed to air at or above ambient temperature. As a result, the Applicant has found that sliding magnetic seals can work successfully in a drawer-type environment and especially in the environments disclosed in the Applicant's abovementioned earlier patent applications.